With the recent advances of biotechnology, various nucleic acids have been found to exhibit bioactive functions in cells. For example, siRNAs (small interfering RNAs) are known to cause degradation of mRNAs of target genes in cells and to thereby inhibit the expression of the target genes (RNA interference). Inhibition of target gene expression by RNA interference is useful for alleviating or treating disease symptoms caused by abnormal expression of specific genes or gene clusters, and therefore development of siRNAs as therapeutic agents is expected. However, in order to use nucleic acids such as siRNAs as therapeutic agents, it is important for such nucleic acids to exhibit their functions in target cells. For this purpose, it is indispensable that a technology to efficiently deliver nucleic acids into target cells be established.
Known technologies to deliver exogenous nucleic acid molecules or genes into cells include treatments of intractable diseases in humans using various viruses including retroviruses, adenoviruses, herpesviruses, etc. However, such treatments involve difficulties because of problems with infectivity, immunoreactivity, productivity and the like. Therefore, non-viral carriers that are free of problems caused by viruses and that can deliver nucleic acid molecules into cells are being developed.
For example, Patent Document 1 has reported a cationic lipid having a specific structure as a non-viral nucleic acid delivery carrier that promotes the delivery of nucleic acids such as siRNAs into cells. However, the cationic lipid reported in Patent Document 1 has a defect in that it exhibits toxicity when administered to cultured cells or organisms. Patent Document 2 discloses a carrier composition containing an amphiphilic compound and polycations as a relatively low-toxicity carrier that can deliver siRNAs into cells. However, the composition reported in Patent Document 2 also has a problem in its toxicity to cells when introducing a sufficient amount of siRNA thereto.
Against this prior art background, the development of a low-toxicity carrier composition for delivery of a nucleic acid that can efficiently deliver nucleic acids such as siRNA into cells is desired.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2002-529439
[Patent Document 2]
Japanese Unexamined Patent Application Publication No. 2005-508394